Pulse generator



Nov. 25, 1958 E. J. CHRZANOWSKI PULSE GENERATOR Filed April 21, 1955 Blocking Oscillcl'ror i l l A; y

WITNESSES INVENTOR Edward J. Chrzunowski 2% M f ZA ATTORNEY United States Patent PULE GENERATOR Edward .i. Chrzanowski, Linthicum, Md, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa, a corporation of Pennsylvania Application April 21, 1955, Serial No. 503,276

Claims. (Cl. 250-27) This invention relates to pulse generators and more particularly to pulse generators which may be used to fire two thyratrons alternately.

In general, the useful life of a thyratron depends upon the operating voltage applied thereto, the magnitude of its anode current, and the frequency at which it is fired. The life span of the thyratron can be materially increased by reducing any of these factors.

It is sometimes necessary or desirable to increase the period of time during which a thyratron modulator or other piece of apparatus will operate without requiring replacement of the thyratron. One method of increasing the period of uninterrupted service in a thyratron modulator consists of operating two thyratrons in parallel. The two thyratrons are fired alternately so that the recurrence frequency of each thyratron is decreased and its useful life increased. By using this method the modulator should operate for a much greater period of time without interruption than it will when only on thyratron is used. Heretofore, it has been common to operate parallel thyratrons with the use of a balanced reactor. A system of this type may be found, for example, in Pulse Generators, MIT Radiation Laboratory Series, volume 5, edited by G. N. Glasol and J. V. Lebacqz, New York, McGraw-Hill Book Co., Inc., 1948. A balanced reactor, however, is inadvantageous since considerable difficulty is encountered in balancing the reactor and avoiding leakage impedance.

It is an object of my invention to provide a new and improved pulse genera-tor.

Another object of my invention lies in the provision of means for firing two parallel thyratrons alternately.

A further object of my invention lies in the provision of a pulse generator for delivering short voltage pulses of high energy content and low impedance alternately to two separate output terminals.

In brief, my invention consists of means for delivering pulses of energy alternately to two separate high voltage modulator thyratrons. The energy pulses are supplied by two pulse-forming networks, one for each thyratron. Each pulse-forming network is charged by a common source of supply voltage and discharged through a low voltage gaseous discharge tube. The operation of the gas tubes is, in turn, controlled by (1) a blocking oscillator which applies trigger pulses to the control grids of the gas tubes, and (2) a bi-stable multivibrator which controls the voltage on the anodes of the gas tubes. The blocking oscillator, multivibrator, gas tubes, and pulseforming networks are so inter-related that when the multivibrator is in one of its two stable states, a first of the pulse-forming networks will discharge through its associated gas tube while the second network is charged by the aforesaid common source of supply voltage; After the first network discharges, the multivibrator shifts to its other stable state. This action reverses the condition of the pulse-forming networks. That is, the second netice 2 work now discharges through its associated gas tube while the first network is charged from the common source of supply voltage. In this manner, alternate high energy pulses of short duration are delivered to the two modulator thyratrons.

Further objects and features of my invention will become apparent from the following detailed description taken in connection with the accompanying single figure drawing which illustrates the invention schematically.

Referring to the drawing, a first pulse-forming network (PFN) 10 has one terminal connected to the positive terminal of a source of anode voltage, not shown, through an anode resistor 12. The other terminal of the pulse-forming network 10 is connected through the primary winding of an output transformer 14 to ground. The secondary winding of the transformer 14 is connected to a first high voltage modulator thyratron, not shown. In a similar manner, a second pulse-forming network (PFN) 16 has one terminal connected to the positive terminal of the aforesaid anode voltage source through an anode resistor 18, and its other terminal connected through the primary winding of an output transformer 20 to ground. A second high voltage modulator thyratron, not shown, is connected to the secondary winding of transformer 20.

The pulse-forming networks 10 and 16, shown in block form, are well known in the art and, in general, consist of inductors and condensers which may be put together in any one of a number of possible configurations. The configuration chosen for the particular purpose at hand depends primarily upon the specific pulser characteristic desired. The values of the inductance and capacitance elements in such a network can be calculated to give an arbitrary pulse shape when the configuration, pulse duration, impedance, and load characteristics are specified. For purposes of the present description, it should be sufiicient to state that the pulse-forming networks serve both as a means for storing the energy of an output pulse and also as pulse-shaping elements. Any pulse-forming networks may be used in the invention which will operate in the manner hereinafter described.

Connected in parallel with pulse-forming network 10 and output transformer 14 is a low voltage thyratron 22. A second low voltage thyratron 24 is connected in parallel with a pulse-forming network 16 and output transformer 20. Trigger pulses from blocking oscillator 26 are applied simultaneously to the control grids of thyratrons 22 and 24 by means of grid resistors 28 and 30.

Alternate charging and discharging of the pulse-forming networks 10 and 16 is controlled by a bi-stable multivibrator 32. The multivibrator includes two triodes 34 and 36, contained within the same envelope. The cathodes of triodes 34 and 36 are both connected directly to ground, and their anodes are connected to the positive terminal of the aforesaid anode voltage source through resistors 12 and 1.8, respectively. The anode of triode 34 is also connected to the anode of thyratron 22, whereas the anode of triode 36 is connected to the anode of thyratron 24. Multivibrator 32 employs direct coupling between the anodes and grids of its two triodes 34 and 36. That is, the plate of triode 34 is connected via resistor 38 and capacitor 40 to the grid of triode 36; and the plate of triode 36 is connected via resistor 42 and capacitor 44 to the grid of triode 34. The voltage divider of resistors 18, 42, and 46 provides a fixed bias for the grid of triode 34; whereas the voltage divider of resistor 12, 33 and 48 provides a fixed bias for the grid of triode 36.

The multivibrator 32 is a circuit possessing two conditions of stable equilibrium. One condition exists when triode 34 is conducting and triode 36 is cut oif; the other when triode 36 is conducting and triode 34 is cut oti. The circuit remains in one or the other of these two conattains ditions until some action occurs which causes the nonconducting tube to conduct. The tubes then reverse their functions and remain in the new condition as long as no plate current fiowsin the cut-off tube. I, The operation of the circuit is based on the fact that when triode 34, for example, is conducting, the negative potential'on its plate is applied via resistor 38 and capacitor 46' to the g'ridfof triode 36*, thereby preventing conduction throu h this tube. Conversely, when triode 36 conduets, the'negative potential'on its plate will be applied through resistor '42 and capacitor '44 to'the grid of triode 34, thereby effecting cut off of this tube.

Operation of the invention is as follows: If it is assumed'that multivibrator 32 is in a condition where triode 36 is conducting and triode 34 is cut ofi, the plates of triode 36 and thyratron 24 will be at a low potential, whereas the plates of triode 34 and thyratron 22 will be at a high potential. Under these circumstances, pulseforrnin'g network ltl will charge through the primary of transformer 14 and resistor 12. Pulse-forming network 16, however, can not charge during this time because of thelow potential 'on' the plate of thyratron 24. When a trigger'pulse from oscillator 26 is applied simultaneously to the'grids'of thyratrons 22 and 24, both thyratrons will fire. 'Pulse forming network will discharge through thyr'ati'on 22 and produce an output pulse across the secondary of transformer 14 which is used to fire the first high voltage modulator thyratron. Since pulse-forming network 16 is not charged during this time an output pulse will not he produced across the secondary winding of transformer 20 when thyratron 24 fires. When thyratron 22 fires, its plate potential is lowered; and this potential is applied through resistor 38 and capacitor 40 to the grid of triode 36;, thereby causing cutoff of triode 36 and initiating eonduction in triode 34. Now that triode 34 is conducting, the plate of thyratron 22 is at a low potential and the plate of thyratron 24 is at a high potential since triode cut off. Under these conditions, pulse-forming network 1 6 will charge through transformer 20 and resistor 18. When the next trigger pulse from blocking oscillator 26 is applied simultaneously to the grids of thyratrons 22 and 24, pulse-forming network 16 will discharge through thy'ratron 24. The resulting reduced plate potential of thyratron 24 is applied through resistor 42 and capacitor 44 to the grid of triode 34, thereby causing cut-off of this triode and initiating conduction of triode 36. This completes one cycle of operation of the circuit. When the next trigger pulse is received from blocking oscillator 26, pulse-forming network 10 will be discharged. The cycle is thus repeated.

It can be seen that the pulse-forming networks 10 and 16 will alternately charge and discharge to provide alternate output voltage pulses across the secondary windings of transformers 14 and 20 to fire the modulator thyratrons.

Although I have described my invention in connection with a specific embodiment, it will be apparent to those skilled in the art that various changes in form and arrangement of parts can be made to suit requirements without departing from the spirit and scope of the invention.

I claim as my invention:

1. In combination with a source of voltage pulses, first and second electron discharge devices, an anode, cathode and control electrode for each of said devices, first conducting means connecting the anode of said first device to the control electrodeof said second device, second conducting means connecting the anode of said second device to the control electrode of said first device, first and second gaseous discharge tubes, an anode, cathode and control electrode for each of said tubes, means for applying said voltage pulses to the control electrode of both of said tubes, the control electrodes of said gaseous discharge tubes being the only circuit elements to which said voltage pulses are applied, means connectingthe cathodes of said discharge devices with'the cathodes of said gaseous discharge tubes, a connection between the anode of said first device and the anode of said first tube, a connection between the anode of said second device and the anode of said second tube, a first pulse-forming network and a load impedance connected between the anode of said first gaseous discharge tube and said interconnected cathodes, and a second pulse-forming network and a load impedance connected between the anode of said second gaseous discharge tube and said interconnected cathodes.

2. In combination, a pair of electron paths, a current controlling device included in each of said paths, means interconnecting said current controlling devices such that conduction in one path will impede conduction in the other path and vice versa, first and second gaseous discharge devices, a control electrode for each of said devices, means connecting said first device to one of said electron paths, means connecting said second device to the other of said electron-paths, a first pulse-forming network connectedto said first device, a second pulse-forming network connected to saidsecond device, and means for applying a control voltageto the control electrodes of said gaseous discharge devices, said last-mentioned control electrodes being the only circuit elements to which saidcontrol voltage is applied.

3. In combination, a pair of electron valves, an input terminal, anoutput terminal and an electrically responsive control element for each of said valves, said valves being characterized by a variation in current flow therethrough in response to variations in a voltage applied between said input terminal and said control element, means interconnecting the input terminals of said valves, a connection between the output terminal of one of said valves and the'control element of the other of said valves and vice versa, first and second gaseous discharge devices, an anode and a control electrode for each of said devices, means connecting the anode of said first device to the output terminal of one of said valves, means connecting the anode of said second device to the output terminal of the other of said valves, a first pulse-forming network connected to the'anode of said first device, a second pulseforming network connected to the anode of said second device, and means for applying a control voltage to the control electrodes of said first and second gaseous discharge devices, said last-mentioned control electrodes being the only circuit elements to which said control voltage is applied.

4. In combination, a pair of electron valves, an input terminal, an output terminal and an electrically responsive control element included in each of said valves, said valves being characterized by a change in current flow therethrough in response to a change in voltage applied between said input terminal and said control element, means connecting the output terminal of one of said valves with the control element of the other of said valves and vice versa, a first pulse-forming network and an impedance element connected between the input and output terminals of one of said valves, a second pulse-forming network and an impedance element connected between the input and output terminals of the other of said valves, a first switching device connected in parallel with said one valve, and a second switching device connected in parallel withsaid other valve, said'first and second switching devices being controlled by' a control voltage applied thereto.

5. In combination, a pair of electron valves, an input terminal, an output terminal and an electrically responsive control element for each of said valves, means interconnecting the input terminals ofsaid valves, afir'st pulseform'ing network and an impedance element connected between the input and output terminals of one of said valves, asec'ond pulse-forming network and an impedance element connected between the input and output terminals of -the otherof said valves, a first switching device co'nn'ec't'ed -in parallel with said one electron valve,

and a second switching device connected in parallel with said other electron valve.

References Cited in the file of this patent 6 Beaufoy Feb. 12, 1952 Cleeton Apr. 8, 1952 Stanton Aug. 5, 1952 Maresca et a1 June 30, 1953 Hollingsworth Jan. 19, 1954 

